The objective of this project is to study the biosynthesis of the surface structures of bacteria - the cell wall and membrane - in relationship to cellular growth and cell division. Streptococcus faecalis ATCC 9790 (S. faecium) will be the primary subject of this study. Where appropriate, studies will be made of other bacterial species, especially those which differ from Streptococci in shape or mode of division, so that generalizations may be made. Cells (and protoplasts) will be grown in a completely synthetic medium under conditions of "balanced" exponential growth, at various rates, and selected "unbalanced" growth conditions. We are particularly interested in the events which occur during the change from one state to the other - for example, after inhibition of DNA, RNA, or protein synthesis, or upon recovery of growth after inhibition of protein antibiotics. We will study events related to cell division cycle. For this purpose we will use cultures selected for synchronized division by a size selection technique utilizing exponential sucrose gradients. We will investigate the dynamics of incorporation, fate and cellular localization of specific radioactive precursors (e.g., L-lysine, and D-alanine for cell walls, chloroform-methanol soluble phosphorus and glycerol for cell membranes), by means of the continuous, pulse, and pulse-chase labeling techniques. We will study the biosynthetic precursors and enzymes involved. Thermosensitive mutants, defective in some aspect of wall and/or membrane biosynthesis, will be isolated and studied. Biochemical and physiological investigations, will be correlated with changes in ultrastructure. BIBLIOGRAPHIC REFERENCES: Cleveland, R. W., Wicken, A. J., Daneo-Moore, L. and Shockman, G. D. The role of lipoteichoic acid in the control of cell wall autolysin in Streptococcus faecalis ATCC 9790. Proc. Soc. Gen. Microbiol. III, p. 32, (1976). Shockman, G. D., Daneo-Moore, L. and Wicken, A. J. On the regulation of cell surface growth and cell division in streptococci. Proc. Soc. Gen. Microbiol. III, p. 5 (1976).